Index: uspace/lib/pcut/src/assert.c
===================================================================
--- uspace/lib/pcut/src/assert.c	(revision 9b201262edcb92c27cf4a25a8379320113426ab7)
+++ uspace/lib/pcut/src/assert.c	(revision 132ab5d1e75253f9bae910b2748a4c13efe7e71f)
@@ -35,6 +35,10 @@
  */
 
-/** We need _BSD_SOURCE because of vsnprintf() when compiling under C89. */
+/*
+ * We need _BSD_SOURCE because of vsnprintf() when compiling under C89.
+ * In newer versions of features.h, _DEFAULT_SOURCE must be defined as well.
+ */
 #define _BSD_SOURCE
+#define _DEFAULT_SOURCE
 
 #include "internal.h"